As described in patent documents WO 2010/141557, US 2011/0130533 and WO 2012/074812, ethylene-based copolymers can be produced by simultaneously producing high density polyethylene or linear low density polyethylene and low density polyethylene in a high pressure reactor. The high density polyethylene is produced in a first reactor or reactor zone in the presence of a molecular catalyst and the low density polyethylene is produced in a second reactor or reactor zone using a free radical initiator. The free radical initiators used previously for this work are typical peroxide initiators which contain polar functionalities. These peroxides decompose to make polar byproducts which are known to deactivate the molecular catalysts resulting in unstable operation and reduced catalyst efficiency, particularly in those processes in which unreacted ethylene and/or polar byproducts from the second reactor zone is recycled to the first reactor zone. Aluminum alkyls can be used to scavenge the polar byproducts and prevent them from deactivating the molecular catalysts, however use of these aluminum alkyls is both economically disadvantageous and can lead to undesired chain transfer reactions.
In one embodiment of this invention, hydrocarbon free radical initiators are used in lieu of peroxide free radical initiators so as to avoid the formation of polar byproducts. Decomposed hydrocarbon free radical initiators have less detrimental impact on the activity and life of molecular catalysts, and this is particularly important in those embodiments in which unreacted ethylene and/or polar byproducts are recycled from the second reaction zone to the first reaction zone. The combination of molecular catalysts with hydrocarbon based free radical initiators can be used to produce interconnected ethylene copolymers with improved catalyst efficiencies and reduced aluminum alkyl requirements. Another advantage of using hydrocarbon based initiators is that the interconnected ethylene copolymer can be produced in a single reactor or reaction zone without having to physically separate the two reaction zones.